This invention relates to the art of fixing or anchoring rails to cross-ties, sleepers or the like.
Rails have traditionally been secured to wooden cross-ties by spikes vertically driven into the tie (today usually into predrilled holes). In recent years, numerous anchoring schemes have been developed which do not rely upon spikes, thus eliminating the vertical opening into the wooden tie. Various other anchoring schemes further enable the use of concrete or steel cross-ties or other understructures into which spikes cannot be driven.
The prior art is replete with proposals. Kelly U.S. Pat. No. 995,541 discloses a steel railway tie with a transverse bolt through the tie generally under the rail and a pair of rigid hook arms for engaging the bolt and the rail flange. The transverse bolt and hook arms cannot be placed until the rail has been set on top of the tie. Only then can the hook arms be slipped over the transverse bolt and tightened in place by turning a nut which is awkwardly positioned beneath the rail. Rigby U.S. Pat. No. 3,065,914 discloses two resilient U-shaped clips that are positioned in oblique holes in the sleeper and held merely by friction. Chapman U.S. Pat. No. 3,322,346 discloses clips designed to be driven into place holding the rail to a single tie bar beneath the center line of the rail. Hall U.S. Pat. No. 3,494,555 discloses two rigid holddown clamps journaled on a transverse rod. Installation requires mechanical or pneumatic tools or machines to exert a significant downward thrust against the pressure plate resting on the rail flange. Novotny U.S. Pat. No. 3,664,584 discloses clip fasteners that engage large protuberances of a specially configured sleeper. Belgian Pat. No. 515,661 discloses a clip that engages the extensions of a transverse rod passing not beneath the foot flange of the rail. One end engages the upper surface of the foot flange and the other end rests upon the top of the tie.
Any new anchoring system must, at least, provide as good or better anchoring than the prior art systems. The requirements for a rail anchoring system are not as simple as they might at first appear. The anchors must resist the lateral movement of the rail so that the gauge is maintained. The anchors should also restrain movement in the longitudinal direction of the rail. The anchors must further secure the rail from twisting along a horizontal axis especially on curves. Finally, the anchors must be designed to withstand vibration and pounding in the vertical direction as well as the movement in the above described horizontal directions. It is known that a rail is subject to an upward force as the vehicle truck approaches and a downward thrust as the wheels on the vehicle truck move thereover. The rail support structure including the anchors must be designed with sufficient flexibility to withstand vibration and pounding. Moreover, any new anchoring system should be at least as easy to install as traditional spikes in wooden rail systems. Preferably, an anchor should be capable of installation with hand tools as well as power means and not easily tampered with thereafter.